This invention relates to a method for and apparatus for the advance indication of the possibility of damage occurring to wheel bearings. The invention is particularly adaptable for rail vehicles, such as railway cars, and to the determination of the possibility of damage to the bearings of the wheel sets of such vehicles. In the following disclosure, it will be apparent that reference to wheel bearings refers primarily, although not exclusively, to the wheel set bearings of rail vehicles.
In order to identify so-called "hot boxes" in railway vehicles, in accordance with known systems warning devices are positioned along the section lines. These warning devices detect the heat radiation, such as infrared radiation, of the wheel bearings of passing vehicles, and convert the radiation to electric signals. These signals are then applied to electronic evaluation systems. The temperature measurement employed in these techniques is a temperature difference measurement, since either a comparison of the temperature between two wheel sets that are opposite one another, or behind one another on the vehicle is made. If the temperature difference between two wheel sets deviates a determined amount from the temperature difference of the remaining wheel sets of the railway vehicle, then a condition of "hot running", or a "hot box" is indicated. The electronic computer evaluates the information from the detectors, and transmits it to an indicator or display at the closest signal box or station. At the same time, an acoustic signal is produced at the signal box or station.
Monitoring systems of this type, employing stationary installations, are no longer adequate, due to the ever increasing speed of the railway vehicles, and it is especially apparent that such systems cannot provide early warnings of possible damage for fast moving vehicles. As the speed of travel of the vehicles increases, the load on the wheel bearings also increases greatly. In order to avoid damage, changes in the characteristics of the mechanical portions of the wheel bearing systems must be ascertained and indicated as early as possible. Such changes result, as a rule, in a change of the temperature of the wheel bearings. Consequently, it is essential to provide a temperature control system that is directly mounted on the vehicle to monitor the temperature of the wheel bearings, and it must include a telecommunication system to indicate the possibility of damage directly to the railway personnel, for example, personnel in the locomotive.
German Patent Publication DT OS2,152,495 discloses a wheel bearing monitoring arrangement, employing a temperature detecting receiver fixed to the vehicle for determining the wheel bearing temperature, the system including means for producing a warning signal when the output of the receiver exceeds a given limit value. In this system, the measuring data relating to the wheel bearing temperatures, for producing the alarm signal, is obtained from at least two separate temperature receivers, in order to provide a difference value which is related to the wheel bearing temperature and the ambient temperature.
The technique of measuring the wheel bearing temperature and comparing it with the ambient temperature as a reference signal is very dependent upon outside influences, especially, for example, in tunnels through which the railway vehicle may be passing, or in regions where there is a large amount of solar radiation. Such known monitoring arrangements, furthermore, do not detect functional, technical changes in the wheel bearings. This can lead to damage of the wheel bearings, even though the measured outer ring temperature of the bearings has a positive correlation to the temperature of the entire bearing, as can be shown by calculations.
The following critical changes can also occur in the wheel bearings: